Resource "aws_ecs_task_definition" still shows as modified each time terraform is applied, "portMappings" is set

[keith-miller]

Terraform Version

Terraform v0.11.10

• provider.aws v1.42.0
• provider.template v1.0.0

Affected Resource(s)

• aws_ecs_task_definition

Terraform Configuration Files

data "template_file" "service_task_json" {
  template = "${file("../../task_definitions/service.json")}"

  vars {
    role           = "gateway"
    cpu            = "${var.gw_cpu_count}"
    mem            = "${var.gw_memory_size}"
    region         = "${var.region}"
    project        = "${var.project_name}"
    env            = "${var.project_environment}"
    ecr_url        = "${var.ecr_url}"
    port           = 8080
    xms            = "${var.gw_xms}"
    xmx            = "${var.gw_xmx}"
    xmn            = "${var.gw_xmn}"
    survivor_ratio = "${var.gw_survivor_ratio}"
    metaspace_size = "${var.gw_metaspace_size}"
  }
}

resource "aws_ecs_task_definition" "service_task" {
  family = "${var.project_role}-${var.project_environment}-task"
  execution_role_arn = "${var.exec_role}"
  network_mode = "awsvpc"
  container_definitions = "${data.template_file.service_task_json.rendered}"
  requires_compatibilities = ["FARGATE"]
  cpu = "${var.desired_cpu}"
  memory = "${var.desired_memory}"
}

service.json

[
  {
    "cpu": ${cpu},
    "memory": ${mem},
    "name": "${role}",
    "image": "${ecr_url}/${project}_${role}:${env}",
    "portMappings": [{
      "containerPort": ${port},
      "hostPort": ${port},
      "protocol": "tcp"
    }],
    "essential": true,
    "environment" : [
      {
        "name": "XMS",
        "value": "${xms}"
      },
      {
        "name": "XMX",
        "value": "${xmx}"
      },
      {
        "name": "XMN",
        "value": "${xmn}"
      },
      {
        "name": "SURVIVOR_RATIO",
        "value": "${survivor_ratio}"
      },
      {
        "name": "MAX_METASPACE_SIZE",
        "value": "${metaspace_size}"
      },
      {
        "name": "APP_ENV",
        "value": "${env}"
      }
    ],
    "logConfiguration": {
      "logDriver" : "awslogs",
      "options": {
        "awslogs-create-group" : "true",
        "awslogs-region" : "${region}",
        "awslogs-group" : "awslogs-${role}-${env}",
        "awslogs-stream-prefix" : "${role}-${env}"
      }
    },
    "mountPoints": [],
    "volumesFrom": []
  }
]

Debug Output

Expected Behavior

No resources should show as changed

Actual Behavior

aws_ecs_task_definition shows as modified which in turn rebuild that resource

-/+ module.gateway.aws_ecs_task_definition.service_task (new resource required)
  container_definitions:               "[...]" => "${var.container_definitions}" (forces new resource)

Steps to Reproduce

1. terraform apply

References

• Resource "aws_ecs_task_definition" shows as modified each time terraform is applied #5323
• aws_ecs_service.my-ecs-service->task_definition" is always shows up as modified #5205

[keith-miller]

#5323 is closed, but I am seeing this still on latest.

[keith-miller]

Would guess it has to do with the string to JSON unmarshaling. I will test without environment set to see if that 'fixes' the issue.

[keith-miller]

It's not environment, it's logConfiguration.options. The order is changing.

[bflad]

We do have a built-in library for ECS Task Definition equivalence: https://github.com/terraform-providers/terraform-provider-aws/blob/master/aws/ecs_task_definition_equivalency.go

It likely requires some additional logic to properly handle that situation. e.g. another sort.Slice()

[keith-miller]

Closing, as this was on me and due to the issue here: hashicorp/terraform#15491

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!